There are 1 campaign, the 1916 one, and 4 scenarios. The scenarios are really diverse in their approach and will definitively bridge a complexity gap if you are too daunted playing a campaign of EAW. Be warned, the 1916 campaign is quite a monster, but definitively manageable with some dedication. Also, the new patch has several very interesting changes, to name a few: Improved retreat logic, artillery can counter fire in battles, smart sorting of units and stacks in the forces list, dozens of events fixes and also additions (yeah!), faster turns.